Dilaton-Axion Wormhole Partition Function Away from the BPS Endpoint

I determine the leading finite-radius correction to the two-boundary response of a charged axion wormhole near its BPS endpoint. With δ=a* squared, exact radial matching in a product axion--dilaton/saxion system gives a boundary eigenvalue that vanishes as O(δ) and an off-diagonal Hessian entry of order O(δ 2). Their combination produces a cross-boundary covariance linear in δ, with a negative first sub-leading correction on the branch studied here. I determine the semiclassical range in which the quadratic approximation remains controlled and identify the first finite-radius angular resonance, δ 2 (δ/δ 0). Under a uniform rescaling of all active charges, the coefficient of the linear cross-boundary response scales as the inverse square of the charge scale. I then average the inverse response over the chiral Gaussian ensemble describing the BPS endpoint. Boundary reduction preserves the hard-edge index. Multiplication by the matched BPS sector weight converts the normalized response into the leading finite-radius two-source coefficient.